The mechanism and experimental study on fracture of thick-bedded backfill roof under high stress

Simply supported beams subjected to uniform was considered mechanical model of backfill roof of underhand drift cut-and-filling stopping, because high-span ratio of stratified backfill was relatively large, there might be some errors in the bearing capacity calculation of material mechanics, through the analysis of the model boundary shape and mechanical distribution characteristic, a semi-inverse method of elasticity was used to obtain stress corrected solutions of load-bearing beam. So three mathematical models were created through different high-span ratios, that were 3:10, 3:5, 3:3, and stress failure curve of elasticity solution was compared with stress failure curve of material mechanics solutions and to validated the correctness of the corrected formula, critical failure equation of backfill roof was derived based on maximum stress criterion, the critical failure curve of backfill was achieved by substituting the mechanics parameters of different stresses into the analytical formulas, and failure modes of backfill roof is found through physical modeling experiment. The results show that the failure of backfill roof is first happening from the center at the bottom of backfill, the final result is that falling arch. Finally, effective measures were proposed to avoid failure of backfill roof.